1. Field of the Invention
The present inventive concept is directed to a method and apparatus to define the depth of a lure that has been deployed behind a fishing vessel while trolling (sport fishing) for various species of fish. It can also be used to measure the temperature of a particular horizon of water. The device is programmed to define the depth and temperature range at a single zone (stratum) of water within a set fixed or programmable amount of time (e.g., 2-minutes with a 5-minute delay).
2. Description of the Related Art
U.S. Pat. No. 5,834,641 discloses a depth gauge with a pressure and temperature sensor and evaluation circuit to record “thermocline” zones at various depths in fresh water lakes. This invention defines temperature zones from a stationary point and is not used “in-line.”
U.S. Pat. Nos. 5,351,538 and 5,469,739 (both McGuire) are in-line devices which use circuitry that calculates the maximum depth trolled over any time period.
U.S. Pat. No. 7,113,449 (Fairbairn) discloses a digital processor based system where the angler physically inputs data parameters such as line type, speed, and weight and the processor outputs depth values. The limitation of this device is simply that it is an estimate.
U.S. Pat. No. 3,786,586 (Swan 1974) is another calculated estimate based upon physical geometries of the fishing line and relative fishing speeds.
U.S. Pat. No. 5,191,719 (Kitt 1993), is a manometric gauge that is calibrated with a depth scale that can be used to determine maximum depth during all types of angling. This device is limited to marking only the maximum depth.
What is needed is an improved way to determine or confirm actual trolling depths so that targeted fish marks observed on a fish finding sonar device can be accurately trolled by deploying lures to the correct horizon.